content: /*
   * Copyright 2011-2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package ix;
  
  import java.util.Iterator;
  
  final class IxScanSeed<T, R> extends IxSource<T, R> {
  
      final IxSupplier<R> seed;
  
      final IxFunction2<R, T, R> scanner;
  
      IxScanSeed(Iterable<T> source, IxSupplier<R> seed, IxFunction2<R, T, R> scanner) {
          super(source);
          this.seed = seed;
          this.scanner = scanner;
      }
  
      @Override
      public Iterator<R> iterator() {
          return new ScanSeedIterator<T, R>(source.iterator(), seed.get(), scanner);
      }
  
      static final class ScanSeedIterator<T, R> extends IxSourceIterator<T, R> {
          final IxFunction2<R, T, R> scanner;
  
          R accumulator;
  
          boolean once;
  
          ScanSeedIterator(Iterator<T> it, R accumulator, IxFunction2<R, T, R> scanner) {
              super(it);
              this.accumulator = accumulator;
              this.scanner = scanner;
          }
  
          @Override
          protected boolean moveNext() {
              if (!once) {
                  once = true;
                  value = accumulator;
                  hasValue = true;
                  return true;
              }
  
              if (it.hasNext()) {
  
                  R v = scanner.apply(accumulator, it.next());
  
                  accumulator = v;
                  value = v;
                  hasValue = true;
                  return true;
              }
  
              accumulator = null;
              done = true;
              return false;
          }
      }
  
  }
  